A methanotrophic community was enriched in a semi-continuous reactor under non-aseptic conditions with methane and ammonia as carbon and nitrogen source. After a year of operation, Methylosinus sp., accounted for 80% relative abundance of the total sequences identified from potential polyhydroxyalkanoates (PHAs) producers, dominated the methane-fed enrichment. Prior to induction of PHA accumulation, cells harvested from the parent reactor contained low level of PHA at 4.0 ± 0.3 wt%. The cells were later incubated in the absence of ammonia with various combinations of methane, propionic acid, and valeric acid to induce biosynthesis of poly(3-hydroxybutyrate) (PHB) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). Previous studies reported that methanotrophic utilization of odd-chain fatty acids for the production of PHAs requires reducing power from methane oxidation. However, our findings demonstrated that the PHB-containing methanotrophic enrichment does not require methane availability to generate 3-hydroxybutyrate (3HB) and 3-hydroxyvalerate (3HV)—when odd-chain fatty acids are presented. The enrichment yielded up to 14 wt% PHA with various mole fractions of 3HV monomer depending on the availability of methane and odd-fatty acids. Overall, the addition of valeric acid resulted in a higher PHA content and a higher 3HV fraction. The highest 3HV fraction (up to 65 mol%) was obtained from the methane–valeric acid experiment, which is higher than those previously reported for PHA-producing methanotrophic mixed microbial cultures.

中文翻译：

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甲烷和奇数链脂肪酸对甲基肌球菌为主的混合培养物对3-羟基丁酸酯（3HB）和3-羟基戊酸酯（3HV）合成的影响

在非无菌条件下，以甲烷和氨气为碳源和氮源，在半连续反应器中富集了甲烷营养群落。经过一年的运作，甲基甲烷菌属（Methylosinus sp。）占从潜在的多羟基链烷酸酯（PHAs）生产者鉴定出的总序列的相对丰度的80％，主要由甲烷喂养。在诱导PHA积累之前，从亲本反应器收集的细胞含有4.0±0.3重量％的低水平的PHA。将细胞在不存在与戊酸甲烷的各种组合，丙酸和氨的后来温育以诱导聚（3-羟基丁酸酯）（PHB）和聚（3-羟基丁酸酯的生物合成共-3-羟基戊酸酯）（PHBV）。先前的研究报道，甲烷异养的利用奇数链脂肪酸生产PHAs要求降低甲烷氧化的能量。但是，我们的发现表明，当存在奇数链脂肪酸时，含PHB的甲烷营养富集不需要甲烷，即可生成3-羟基丁酸酯（3HB）和3-羟基戊酸酯（3HV）。取决于甲烷和奇脂肪酸的可用性，通过各种摩尔分数的3HV单体，富集可产生高达14 wt％的PHA。总体而言，戊酸的添加导致较高的PHA含量和较高的3HV分数。从甲烷-戊酸实验中获得最高的3HV分数（最高65 mol％），高于先前报道的生产PHA的甲烷营养混合微生物培养物的3HV分数。